The present disclosure relates to a solid-state imaging device, a method of producing the solid-state imaging device and electronic apparatus. Particularly, the present disclosure relates to a solid-state imaging device having a charge accumulation portion in a unit pixel, a method of producing the solid-state imaging device and electronic apparatus.
A solid-state imaging device such as a CMOS image sensor, which is a kind of solid-state imaging device of an X-Y addressing scheme, performs an operation of sequentially scanning and reading light charges generated and accumulated in a photoelectric conversion portion every pixel or every row. In the case of this sequential scanning, that is, in the case of adopting a rolling shutter as an electronic shutter, it is not possible to share the exposure start time and exposure end time to accumulate light charges, in all pixels. Therefore, in the case of the sequential scanning, there is a problem that distortion is caused in a taken image at the time of taking an image of a moving subject.
In the case of taking an image of a subject that moves at high speed in which that kind of image distortion is not allowed, or in the case of the sensing use requesting synchronism in a taken image, a global shutter to execute the exposure start and the exposure end at the same timings with respect to all pixels in a pixel array portion is adopted as an electronic shutter. To realize this global shutter, as an area to accumulate light charges separately from a photodiode which is a photoelectric conversion portion, that is, as a charge accumulation portion, for example, a flush-mounted MOS capacitor is set (for example, see Japanese Patent No. 3874135).
However, when a flush-mounted MOS capacitor receives all light charges generated and accumulated by photoelectric conversion in a photodiode at the time of global shutter, the flush-mounted MOS capacitor requests a saturated charge amount equal to or larger than that of the photodiode. To put it the other way around, taking into account the same unit pixel size, when there is a flush-mounted MOS capacitor in a unit pixel, since the photodiode area significantly becomes small, there is a problem that the saturated charge amount of the photodiode becomes small.
As its countermeasure, there is suggested a technique of accumulating light charges, which are generated by photoelectric conversion in a photodiode, in both the photodiode and a flush-mounted MOS capacitor (for example, see Japanese Patent Laid-Open No. 2009-268083). According to this related art, the saturated charge amount is a sum of the saturated charge amount of the photodiode and the saturated charge amount of the flush-mounted MOS capacitor.
However, even in the related art disclosed in Japanese Patent Laid-Open No. 2009-268083, the saturated charge amount is much smaller than that of a CMOS image sensor without a global shutter function. This is because, to realize the global exposure, it is requested to add not only a charge accumulation portion (in the case of the related art, flush-mounted MOS capacitor) but also a transistor into a unit pixel. As a result, it causes degradation of the image dynamic range.
Meanwhile, to increase the saturated charge amount and widen the dynamic range, separately from the related art to realize the global exposure, there is a possible case where a capacitor of a larger capacity value per unit area is used as a charge accumulation portion instead of a flush-mounted MOS capacitor.